1. Field of the Invention
The present invention relates to an optical deflection element deflecting a light and an optical switch outputting an inputted optical signal to a desired channel.
In recent years, a photonic network is increasingly demanded for high-speed driving and high-capacity more than ever, in which the optical signals have had a broadband and been multiplexed, and hence the transmission equipment of the photonic network is also demanded multichannel and high-speed driving as well. Also, an optical cross-connect equipment serving as a node of the photonic network is required to increase the number of channels and to switch at higher speed, and hence an optical switch for example of Japanese Patent Application Laid-Open No. Hei3-87817 (Patent Document 1) is needed as an alternative to current optical cross connect equipment using a mirror and supported by a micromachine such as MEMS (Micro Electro Mechanical Systems).
An optical switch using an optical waveguide is necessary to adjust an optical deflection angle along with the advance toward the high-speed driving and multichannel. For the optical switches using the optical waveguide, the use of so-called photonic crystals is closely watched, the photonic crystal being composed of plural kinds of substances having different refractive indexes and aligned periodically. The photonic crystal is a crystal structure composed of plural media having different refractive indexes aligned periodically. The photonic crystal is expected as an element technology capable of reducing the size of conventional optical devices to several microns. Inside the photonic crystals, depending on the alignment period, shape, refractive angles, and so forth, the photonic band structure is modulated in the same manner as the band structure of electrons in semiconductors or the like, so that a peculiar band structure is formed. For instance, a forbidden band referred to as a photonic band gap is formed in the vicinity of a Brillouin zone, and a light cannot exist inside the photonic crystal of such a frequency band. Further, the photonic band in the vicinity of the photonic band gap is largely modulated and the surface that disperses frequency differs largely from those of common optical crystals. For instance, there has been a report in H. Kosaka et al. Phys. Rev. B 58, R10099 (1998); H Kosaka et al. Appl. Phys. Lett. 74, 1212 (1999); H Kosaka et al. Appl. Phys. Lett. 74, 1370 (1999) (Non-Patent Document 1), saying that a large optical deflection called “super-prism effect” is observed by selecting a light of an appropriate wave length for the surface that disperses frequency and formed by the wave number of the photonic band.
As specific examples of the optical switch using the photonic crystals, for example, there are those technologies that are disclosed in Japanese Patent Application Laid-Open No. 2002-350908 (Patent Document 2), Japanese Patent Application Laid-Open No. 2002-303836 (Patent Document 3), and Japanese Patent Application Laid-Open No. 2003-215367 (Patent Document 4).
In Patent Document 2, there is disclosed an invention of a principle that a deflection angle is adjustable by applying an energy such as voltage to photonic crystals.
In Patent Document 3, there is disclosed an invention that forms an optical path by forming a line defect waveguide in photonic crystals composing a core of an optical waveguide.
In Patent Document 4, similarly to Patent Document 3, there is disclosed an invention in which the core of the optical waveguide is formed by photonic crystals and a portion not satisfying the alignment having the above-described periodical structure is formed in the photonic crystals to thereby use the portion as an optical path.
2. Description of the Related Art
In the optical switches employing the above-described conventional photonic crystals, it is possible to delineate an optical path and to obtain a large deflection angle, however, there is a problem that the precision of adjusting the deflection angle is not so high. The recent demands for high-speed driving and multichannel in the optical switches are increasing further, and in order to sufficiently respond to the demands, the precision of adjusting the deflection angle needs to be improved substantially, and thereby a technology for that purpose is sought for under the present set of circumstances.